This depends on a lot of factors-
1) How far your computer is away from modem.
2) How much junk you have on your computer.
3) Your average ISP(Internet Service Provider) speed for that area.
4) How much RAM(Random Access Memory) your computer has.
5) How many registry errors you have.
Some Tips and Tricks-
A good program for file cleaning and registry error fixing is CCleaner(Google It).
Try plugging your computer directly up to modem via Ethernet Cable if you can.
If your RAM is below 1 GB, which it shouldn't, I would suggest upgrading that or betting a new computer.
One more thing-
Your computer could also have viruses. A free program I recommend would be "AVG Anti-virus 2011 Free"
Hope This Helps!
-Anonymous